INDUSTRIAL PROGRESS DURING THE YEAR 1875. Jin 



either major or minor, corresponding to a speed for each of 

 between thirty-five and forty miles an hour. 



HEAT. 



On the subject of Heat, Cailletet has further studied the ef- 

 fect of pressure on combustion, the experiments being made 

 up to three hundred atmospheres. He finds that while the 

 luminosity of a flame increases under pressure, the activity 

 of the combustion actually diminishes ; the temperature aug- 

 ments, but the oxidation lessens. An alcohol flame, ordina- 

 rily so pale, becomes as bright as that of a candle at twenty 

 atmospheres. A candle flame under these conditions gives 

 more light, but the wick soon becomes smoky from imperfect 

 combustion that which is gained on the one side being lost 

 on the other. 



Violle has called attention to the thermo-diffusion experi- 

 ments of Feddersen and Dufour (which are properly such, 

 since the diffusion of a gas through a porous diaphragm 

 causes a rise of temperature on the side of the entering gas, 

 and a difference of temperature on the two sides of such a 

 diaphragm causes a diffusion of gas), in order to explain an 

 experiment of Dufour, in which he used air in different hy- 

 grometric states on the two sides of the diaphragm, and ob- 

 served the diffusion. Violle believes that the true explana- 

 tion of this result is to be found in Merget's experiments, in 

 which a porous cell, filled with pumice in fragments, and 

 closed by a cork through which a tube passes, the whole be- 

 ing well moistened, develops, when exteriorly heated to a 

 dull red heat, simply from the surface evaporation, a pressure 

 of air in its interior of three atmospheres. Experiments of 

 his own show how extremely sensitive is this apparatus to 

 changes of temperature. The practical importance of these 

 fricts is very great. Our clothes, the stones of our houses, 

 the very soil itself, w r hen heated after previous moistening, 

 act exactly like the apparatus of Merget, with an activity 

 truly surprising. In animals this gaseous movement plays 

 its part in respiration ; but in plants, especially in aquatic 

 plants, it is seen in full activity, JSfelumbiwn speciosicm, for 

 example, throwing from its stomata half a liter of air per 

 minute, solely through this action going on in its leaves. 



Berthelot has published an important research, in which he 



